1. Field of the Invention
The present invention relates to a lubricant feed system in the journal of a crankshaft for an internal combustion engine.
2. Description of the Related Art
The journal of a crankshaft is generally supported by bearing supporting portions respectively formed in a cylinder block and caps. Such bearings, in the form of half shells, are arranged on the bearing supporting portions of the cylinder block and the caps. With this arrangement, lubricant in an oil main gallery is fed to the bearings via given passages.
Japanese patent publication No. 58-27124, for instance, discloses a system for feeding lubricant to such a journal. In the disclosed system, oil grooves are formed at bearing supporting portions in a cylinder block and annular grooves are formed at the inner peripheral surfaces of the bearings. The oil grooves are communicated with the annular grooves via apertures formed at the bearings. Further, an oil main gallery is provided in the cylinder block and the lubricant is fed to the oil grooves of the bearing supporting portions in the cylinder block and the bearings arranged thereon. The inner peripheral surfaces of the bearings are made flat to ensure sufficient bearing area between the bearings in the caps and the journal to prevent seizing thereof.
However, no grooves are formed to feed the lubricant from the oil main gallery to the bearing supporting portions in the caps and the bearings arranged thereon. It is for this reason that the bearings to which explosive loads are applied are not sufficiently cooled.